Treatment of textile dyeing wastewater by hydrogen peroxide and ferrous ions

The results of investigations on the applicability of Fenton reagent in the treatment of textile dyeing wastewater were discussed. The optimum conditions and efficiency of the method were determined, taking as an example three types of wastewater produced while dyeing cotton, polyacrylonitrile and polyester. The effect of the type and dose of coagulant was investigated. Two types of iron (II) salt were used: sulphate (FeSO4 x 7H(2)O) and chloride (FeCl2 x 4 H2O); to adjust the pH of the wastewater, a 1 % solution of calcium oxide (CaO) was used. The process of pollutant decomposition which took place in the wastewater under the influence of hydrogen peroxide alone at different concentrations was investigated. When the Fenton reagent was used both for sulphate and iron (II) chloride, the optimum doses of the two salts and hydrogen peroxide were determined. It was found that the tested dyeing wastewater revealed high susceptibility to treatment using a combined action of ferrous salts and hydrogen peroxide. The main parameters of wastewater, i.e. the colour threshold number, chemical oxygen demand and anionic surfactants, were reduced by dozens of percent. Investigations of the wastewater after treatment showed a remarkable increase in susceptibility to biodegradation.